Trust, as a philosophical concept in education, seems largely taken for granted, either because it is embedded in other discourses, or is self-evidently assumed to be one on which there is general agreement and understanding. Its associated notions, such as confidence and belief, have counters in such concepts as disappointment and betrayal. These various notions come to the fore in interpersonal relations that require openness and self-critique. Critically reflective practice in professional teaching contexts is one such example, where openness means that people involved may experience vulnerability. I will argue that the development of critically reflective practice is impossible in the absence of trust, and will take the position that trust requires the trustor to be vulnerable to betrayal. I draw on some findings of an ongoing research study in a selection of New Zealand schools, during which I have found that many participants attempt to connect reflective practice to appraisal, a move which, in light of what I present in relation to trust, I argue should be resisted.